Conventionally, the amount of intake air to an internal combustion engine such as an automobile engine is adjusted by opening or closing throttle valves arranged in air intake passages. When the throttle valves are opened rapidly, large amount of air is sucked in a short period, so that unusual sounds or noises are caused in surge tanks, intake manifolds and the like connected to or arranged at downstream of the throttle valves.
In order to suppress such unusual sounds, a structure comprising a net arranged at downstream of the throttle valve is proposed (for example, see reference 1).
Hereinafter, one of the conventional devices for reducing noises caused during the air intake operation is explained as referring to drawings.
FIG. 6 is a schematic view of an air intake passage of an internal combustion engine. FIG. 7 is a schematic perspective view of an air intake noise reducing device. FIG. 8 (a) shows a cross-sectional view along C-C line in FIG. 7 and FIG. 8 (b) shows a cross-sectional view along D-D line in FIG. 7.
An air intake noise reducing device 101 is arranged at a downstream position from a throttle valve 110 in the vicinity where the device can affect air streams from the throttle valve 110. The air intake noise reducing device 101 is arranged at a connecting portion of an air intake passage 100, where two pipe members, for example a throttle body and a surge tank are abutted each other, so that the air intake noise reducing device is held by both ends of the pipe members.
A reference numeral 102 is an annular gasket. Airtightness at the connecting portion is secured by the annular gasket 102, which is held by end surfaces of the throttle body and the surge tank.
A reference numeral 103 is a net for reducing the air intake noise. Air flowing through the air intake passage 100 is dispersed and rectified by the net 103, so that the air intake noise is reduced. A metal mesh and the like are employed as the net 103.
As shown in FIG. 7 and FIG. 8 (a), the gasket 102 and the net 103 are connected each other by inserting protruded portions 104 formed around the periphery of the net 103 into the gasket 102. Further, as shown in FIG. 8 (b), sometimes an outer rim 105 for connecting protruded portions 104 together, passes through the gasket 102.
The net 103 and the gasket 102 are formed into a one-pieced device such that the protruded portions 104 and the outer rim 105 are fixed to the gasket 102 by an adhesive.                Reference 1: Japanese laid open patent No. 11-141416        